Improvement in bridges



PATENT" OFFICE.

JOHNV zELLwnennQor LoUIsvILLE, KENTUCKY.'

' iMPRAov'EMENT iN BRIDGES;

Specification forming part of Letters Patent No. 125,244, dated April 2, 1872.

SPECIFICATION. I, JOHN ZELLWEGER, of Louisville, county of J elierson, State of Kentucky, have inventedv certain improvements in the relative position of arches in archbrid ges or viaducts, of which the following is a specification: y

Nature and Objects of the Invention.

Description of the Accompanying Drawing.

Figure l is a side elevation of a bridge or part of a viaduct, showing the shape ofthe arch. Fig. 2 is a vertical section across the bridge through the middle m, showing the inclination ofthe arches and the bracing of same. Fig. 3 isa top view of the bridge, showing again the spread oi' the arches, the lateral bracing, track arrangement, and foundations. Fig. 4 shows the inclined position of posts e. Fig. 5 shows the inclined position of posts d. Fig. 6 and Fig. 7 are elevations ot' knee-casting o. Fig. 8 is an elevation of crown-casting fm.

General Description.

The use of arches under grade for bridges or viaducts, in all cases where there Vis a great diiierence of height between the grade of a road and the ground or high water, allows of a very material reduction of the expensive masonry in piers and abutments in comparison with trussed or girdenbridges, from the fact that all the strain caused from constant and movable load is directly carried to the ground, its natura-l receiving point. In order to give to an arch-bridge or viaduct the greatest stability with the least amount oi' material, I i11- cline the two archcsA andB toward each other throughout their whole plane, so that their apices are nearest and their bases furthest from each other. For deck-bridges, where the roadway passes through the crown m, or rst joint n thereof, the distance between the arches 011 top is governed by the width of the roadway and by the lateral stiffness; while the distance at the bottom, with a given inclination, increases with the height of the structure. The lateral bracing has to be made strong enough to meet irregularities. The points m, n, o, and p should be on a regular curve of the second degree; if they are on a parabola they hold each other in equilibrium when equally loaded. The inclined position does not aiect this law, as all side strain is transmitted from one arch to the other by the lateral bracing. The duty of the girder g is to distribute the moving load equally on all the bearing points of one-half of the span and to resist the upward tendency of the unloaded part of the span. It therefore acts alternately upward and downward and has to be constructed accordingly. The arch-braces a, b, and c are chords between the points m, n, o, and p; these braces, as well as the posts d, e, and f, can be out of wrought-iron, cast-iron, or wood-out of one or more pieces ;y wrought-iron in the shape of hollow cylinders seems to be preferable to castiron ofthe same shape or any other combination of rolled iron. Channel-beams could also be used advantageously. The joints m, n, and o, bearings q, and bases p are made out of castiron. The joint-castin gs (knee-castin gs) n and o, for hollow wrought-iron posts, have the shape shown in the drawing Fig. 6 and Fig. 7 for casting o.

All the joint castings between the crown and spring ofthe arch are similar in construction and differ only in the relative angles between the posts and braces.

This improvement could be extended to through-bridges, arched or trussed, in which case the crowns of the arches or top-chords come as near as to touch each other, or as to form one topchord. For arch-bridges of this kind wire rope might be successfully used for the suspension of the roadway. Each beara ig point of a, girder could be hung up to three joints of the arch.

Claim.

their whole plane, combined with the girders q q, and suitable accessory supports and connections1 as herein described.

JOHN ZELLWEGER.

Witnesses RUDOLFH FINK, GUsHrrAN QUARRIER. 

